[Reference: https://www.privacy-regulation.eu/en/recital-143-GDPR.htm,  The Court of Justice of the European Union (CJEU) is the judicial body of the EU that makes decisions on issues of EU law and enforces European decisions either in respect to actions taken by the European Commission against a member state or actions taken by individuals to enforce their rights under EU law. The CJEU consists of two courts: the Court of Justice and the General Court. The CJEU ensures the uniform interpretation and application of EU law across the EU and settles disputes between EU institutions, member states, and individuals., According to the EU Treaties, EU Member-States’ courts may – or, in case no appeal from their decisions is possible, must – ask the CJEU to rule on the interpretation and validity of disputed provisions of EU law. Such decisions are known as preliminary rulings, by which the CJEU expresses its ultimate authority to interpret EU law and which are binding for all national courts in the EU when they apply those specific provisions in individual cases. Since May 2018 – when the GDPR became applicable across the EU -, the CJEU has played an important role in clarifying the meaning and scope of some of its key concepts. For instance, the Court notably ruled that two parties as different as a website owner that has embedded a Facebook plugin and Facebook may be qualified as joint controllers by taking converging decisions ( Fashion ID case ), that consent for online data processing is not validly expressed through pre-ticked boxes ( Planet49 case) and that the European Commission Decision to grant adequacy to the EU-US Privacy Shield framework is invalid as a mechanism for international data transfers, and supplemental measures may be necessary to lawfully transfer data outside of the EU on the basis of Commission-vetted model clauses (in the Schrems II case )., Therefore, to receive a preliminary interpretation on provisions of the GDPR, a national court will refer its case to the Court of Justice of the European Union, which is the ultimate authority on EU law and the GDPR., References:, GDPR, Court of Justice of the European Union, Court of Justice of the European Union - International Association of Privacy Professionals, Judicial enforcement of EU law | European Foundation for the Improvement of Living and Working Conditions, [Competences of the Court of Justice of the European Union], ]